A high fat diet leads to overeating because of faulty brain signaling

http://www.eurekalert.org/pub_releases/2015-09/e-ahf091615.php

Public Release: 21-Sep-2015
A high fat diet leads to overeating because of faulty brain signaling
Offering low fat foods could help prevent obesity, say researchers
Elsevier

Defective signaling in the brain can cause overeating of high fat foods in mice, leading to obesity, according to one of the first research articles published in the new open access journal Heliyon. The body controls food intake by balancing a need for food to survive with a desire for food for pleasure. By shifting the balance between these systems, defective brain signaling can cause pleasure to take over, resulting in overeating and obesity.

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"We have always been struck by how much animals - and even people - will over-consume tasty high-fat foods, even though they might be technically feeling full," said Dr. Aurelio Galli, one of the authors of the study. "A high fat diet causes people to eat more, which ultimately impairs the ability of obese people to successfully control their caloric intake, lose weight and maintain weight loss. We have conducted several studies trying to understand why a high fat diet has this effect."

Worldwide, obesity has more than doubled since 1980. Today around two billion people are overweight, and 600 million of these are obese. A number of factors contribute to the obesity epidemic, including economic stresses, changes in the built environment and changing food trends.

Biologically, obesity is the result of defects in the central nervous system that mean the body can't match its energy intake through food with its energy expenditure. The amount we eat is controlled by survival and reward (hedonic eating) the body's metabolism and our pleasure senses, like taste and smell. When specific signals in the brain are impaired, these two systems can fall out of balance, resulting in overeating.

The new study reveals a novel mechanism behind overeating high fat foods for pleasure. A specific signaling pathway in brain cells that control motivation, movement and attention determines the amount of high fat foods consumed. When the signaling is defective, the person only overeats high fat foods.

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"Our findings reveal a system that is designed to control eating of rewarding foods that are high in fat and possibly sugar," said Dr. Galli. "This system can be hijacked by the very foods that it is designed to control. Eating a high-fat or high-carbohydrate diet feels rewarding, but also appears to cause changes in the brain areas that are involved in controlling eating, by causing for example insulin resistance. Our study shows that when specific signaling in these areas of the brain is disrupted, it leads to a vicious cycle of increasing, escalating high-fat diet intake that likely further cements changes in these brain areas."

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